The present disclosure relates generally to dual-energy imaging and, in particular, to techniques for producing and processing dual-energy images with a mobile dual-energy imaging system having a portable flat-panel digital detector.
Medical diagnostic and imaging systems are ubiquitous in modern health care facilities. Currently, a number of modalities exist for medical diagnostic and imaging systems. These include computed tomography (CT) systems, X-ray systems (including both conventional and digital or digitized imaging systems), magnetic resonance (MR) systems, positron emission tomography (PET) systems, ultrasound systems, nuclear medicine systems, and so forth. Such systems provide invaluable tools for identifying, diagnosing and treating physical conditions and greatly reduce the need for surgical diagnostic intervention. In many instances, these modalities complement one another and offer the physician a range of techniques for imaging particular types of tissue, organs, physiological systems, and so forth.
Digital imaging systems are becoming increasingly widespread for producing digital data that can be reconstructed into useful radiographic images. In one application of a digital imaging system, radiation from a source is directed toward a subject, typically a patient in a medical diagnostic application, and a portion of the radiation passes through the subject and impacts a detector. The surface of the detector converts the radiation to light photons, which are sensed. The detector is divided into an array of discrete picture elements or pixels, and encodes output signals based upon the quantity or intensity of the radiation impacting each pixel region. Because the radiation intensity is altered as the radiation passes through the subject, the images reconstructed based upon the output signals may provide a projection of tissues and other features similar to those available through conventional photographic film techniques. In use, the signals generated at the pixel locations of the detector are sampled and digitized. The digital values are transmitted to processing circuitry where they are filtered, scaled, and further processed to produce the image data set. The data set may then be used to reconstruct the resulting image, to display the image, such as on a computer monitor, to transfer the image to conventional photographic film, and so forth.
Dual-energy (DE) radiography involves the acquisition of two X-ray images at different energies within a relatively small time interval. The two images are then used to decompose the imaged anatomy and create soft-tissue and bone images. Existing digital radiography (DR) image acquisition and processing techniques were not designed for DE radiography. In addition, the application of DE imaging to mobile DR imaging systems adds several unique challenges. For example, in a mobile DR imaging system, the spatial location of the detector is not always known relative to the X-ray source, as in a fixed permanent DR imaging system. Additionally, the detector may not be mechanically fixed relative to the X-ray source and may move slightly whenever the patient moves. As a result, misalignment may occur between the X-ray source and the detector. Furthermore, mobile DR imaging systems frequently are used to obtain images of patients that are too sick to move. Consequently, these patients frequently cannot hold their breaths very easily, if at all. As a result, artifacts are created in the image when the lung volume changes between the first and second exposure.
Accordingly, techniques are needed to overcome the problems associated with mobile DR imaging systems. The techniques described herein are intended to solve one or more of the problems associated with mobile DR imaging systems.